The present invention relates to a sensor installation structure for industrial vehicles.
In industrial vehicles such as a fork lift, the swing amount of the rear axle is restrained by a controller to prevent the excessive inclination of the vehicles due to centrifugal force when turning. The control is executed based on the centrifugal acceleration and the yaw rate that act on the vehicles. The centrifugal acceleration is calculated from the steering angle (or wheel angle) of the wheels and the speed of the vehicles.
A method to calculate the wheel angle is described in Japanese Examined Patent Publication No. 4-24270. The forklift described in that publication has a power steering apparatus. The power steering apparatus includes a steering shaft rotated by a steering wheel and a valve unit connected to the shaft. The valve unit supplies hydraulic oil to and drains the oil from a cylinder in accordance with the rotation of the steering shaft. Piston rods protrude from both ends of the cylinder, and each piston rod is connected to a wheel. The cylinder is driven by hydraulic oil from the valve unit to steer the wheels. The piston rod motion is detected by a stroke sensor, and the wheel angle is calculated based on the detected value.
However, the linear movement of the piston rods have to be converted to the wheel angle, and the piston rod movement is not proportional to the wheel angle. This is because the piston rod linear movement is converted to the wheel rotation movement via a transmission mechanism such as a link. Accordingly, determining the wheel angle with respect to the piston rod movement is not easy.
To solve this problem, the wheel angle may be directly detected using a potentiometer. The potentiometer detects the rotation angle of a kingpin rotated with the wheels. The kingpin is pivotally supported by an upper bracket that constitutes an axle beam. The potentiometer is provided on the upper bracket, that is, over the kingpin, to detect the kingpin rotation angle.
According to this construction, since the upper bracket is located in a wheel well, the potentiometer is also located in the wheel well. Accordingly, the potentiometer is exposed to foreign substances such as pebbles and water spattered by the wheels. To protect the potentiometer from such foreign matter, the potentiometer is covered by a case made of hard material such as metal. The case has an opening for passage of the lead wires connected to the potentiometer.
However, since the interior of the wheel well is exposed to fine dust and rain water in addition to pebbles, these fine substances reach the potentiometer through the opening. This lowers the durability and accuracy of the potentiometer.
Accordingly, the objective of the present invention is to provide a sensor installation structure to ensure the protection of the sensor.
To achieve the above objective, the present invention provides a housing structure for protecting a vehicle sensor, wherein the sensor is provided on a structural member that is exposed to the environment, and wherein lead wires are connected to the sensor. The housing structure includes a cover fixed on the member to cover the sensor, wherein, the cover has an opening for permitting the passage of the lead wires, and a sealing material located between the cover and the sensor to seal the sensor.
The present invention further provides a cover for covering a sensor installed on a vehicle structural member, wherein the structural member is exposed to the environment, and wherein the cover has an opening for permitting the passage of lead wires of the sensor and a through hole, which is formed in a wall of the cover, for facilitating a sealing process for sealing the sensor.
The present invention also provides a method for installing a sensor in a vehicle, wherein lead wires are attached to the sensor. The method includes fixing the sensor on a structural member of the vehicle, covering the sensor with a cover, wherein the cover is exposed to the environment, and wherein the lead wires pass through an opening in the cover, charging a fluid sealing material inside the cover through the cover opening, and hardening the charged sealing material.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.